Loudspeaker arrangement



'LOUDSPEAKER ARRANGEMENT Filed Dec. 17, 1937 by ,F%

Patented July 4, 1939 UNITED STATES PATENT OFFICE 2,164,977 nounsrnma ARRANGEMENT Alfred Wiessner, Berlin, Germany, assignor to O. Lorenz Aktiengesellschaft, Berlin-Tempelhof,

Germany, a company Application December 17, 1937, Serial No. 180,338 In GermanyDecember 22, 1936 Claims.

In the operation of loudspeakers it is in certain cases desirable to have their circuits closed from a remote station, thus dispensingwith a local attendant. Such is the, case, for instance,

-5 if .the loudspeakers are to operate at a desired time only, requiring stantly.

In accordance with the invention a sound emitting apparatus of the loudspeaker type shall be them to be actuated inw operable-from a remote transmitting station and by means of predetermined signals, the communications and other signals intended for transmission being conveyed to the sound emitting apparatus with the aid of a carrier frequency.

16 According to a further feature of the invention part of the output energy of this apparatus is used for obtaining a revertive indication and for supervision. It is of advantage here that a single line may be utilized for both feeding such 29 apparatus and permanently supervising the operation thereof.

'The invention will be understood from the following description, reference being had to the accompanying drawing which shows a diagram 25 of one embodiment thereof. I

i denotes a sound emitting apparatus which is to be attended to and supervised from a remote station H. The apparatus I here shown by way of example comprises an amplifier and rectifier o 2, an output amplifier 3, a loudspeaker l or a number thereof, a high pass filter 5, anda low pass filter 6. Station I2 is a transmitting station which comprises a high frequency transmitting device I, a high pass filter 8, a low pass 5 filter 9 and a supervision device Ill. The stations I, 12 are interconnected by a line H of any desired or suitable length.

The operation is as follows.

In order to effect a transmission, apparatus l is at first rendered ready for operation. For instance, a predetermined signal, such for example as a low frequency current of 50 cycles per second, is impressed upon line H from station l2. Such current acts to render the high frequency re- 5 ceiver or rectifier 2 ready for operation, for instance by energizing a tuned relay orthe like. In order now to operate the sound emitting apparatus I a modulated carrier frequency is conveyed thereto from device I over the filters 8, 5. In apparatus I this frequency causes the final stage, for instance, of the sound amplifier to be switched in or acts to close the circuit of the loudspeaker 4 itself. Thereupon the transmission of communications, effected by means of the carrier fre-.

55 quency modulated by device I, takes place. This frequency is in a well-known manner conveyed over the high pass filter 5 to device 2 and amplified by device 3, being then emitted by loudspeaker 4. Part of the voice frequency is derived at a point in advance of the loudspeaker 5 and is carried back to line ll over low pass filter 6. At station l2 the voice frequency is taken from line H over filter 9 and is indicated by supervision device l0 acoustically or optically.

To employ a carrier frequency for feeding the 10 loudspeaker apparatus involves the great advantage that the speech on its passage along line H is not liable to distortion. By having the voice frequency indicated at station H the advantage is obtained that here the'voice frequency amplitude of the loudspeaker can be ascertained by direct measurement, the attenuation which this low frequency energy undergoes on its passage along line ll being small as compared with that of the high frequency energy. If the high frem quency energy on its passage along line H is too I much attenuated, or if the intensity of the emitted sound is found to be too low, then station I! will be able in a simple manner to obtain a readjustment by increasing the transmitting amplia tude.

Instead of the revertive indication effected by means of a voice frequency, an indication on a carrier frequency different from the transmitting wave may be provided. For instance, with a.

a transmitting frequency of 50 kilo-Hertz a revertive indication on a frequency of 10 kilo- Hertz may take place, this frequency being modulated with the output energy of the loudspeaker 1. Loudspeaker arrangement comprising! a transmitter including means for producing a modulated carrier current and means for producing a control current; a receiver remote from said transmitter and including a sound emitting ap paratus, means for demodulating said carrier current, means responsive to said control current and adapted to render said receiver operative; means to convey said carrier current and said control current in one direction from the transmitter to the receiver, and further means for conveying a' revertive signal in the opposite direction;

2. A loudspeaker arrangement comprising a sound emitting apparatus, a transmitting station remote therefrom, means in this station for producing a modulated carrier i'requency, means in the same station for producing energy adapted to switch-in the sound emitting apparatus, a line interconnecting this apparatus and said station and adapted to convey the said switch-in energy and carrier frequency to the sound emitting apparatus, and means for causing energy, adapted to efl'ect a revertive indication, to be conveyed from this apparatus to the transmitting station. 3. A loudspeaker arrangement comprising a sound emitting apparatus. a transmitting station remote therefrom, means in this station for producing a modulated carrier frequency, means in the same station for producing a voice frequency adapted to switch-in the sound emitting apparatus, a line interconnecting this apparatus and said station and adapted to convey said carrier frequency and voice frequency to the sound emitting apparatus, and means to cause part of such voice frequency to be carried back into the said line, this part being adapted to effect a revertive indication.

4. An arrangement according to claim 2, having means to produce a second carrier frequency as the energy adapted to eflect the said revertive indication.

5. An arrangement according to claim 1, having a high frequency portion adapted to be cut in by low frequency energy and in remote control fashion, and a low frequency portion adapted in remote control fashion to be cut in by a carrier frequency modulated with a predetermined frequency.

ALFRED WIESSNER. 

